U.S. patent number 9,853,559 [Application Number 15/123,564] was granted by the patent office on 2017-12-26 for power conversion device with reduced current deviation.
This patent grant is currently assigned to DAIKIN INDUSTRIES, LTD.. The grantee listed for this patent is DAIKIN INDUSTRIES, LTD.. Invention is credited to Nobuo Hayashi, Takurou Ogawa, Morimitsu Sekimoto, Tomoisa Taniguchi, Eiji Tooyama.
United States Patent |
9,853,559 |
Taniguchi , et al. |
December 26, 2017 |
Power conversion device with reduced current deviation
Abstract
Disclosed herein is a power conversion device including a
storage and a power conversion controller. The storage stores
multiple values, each correlated to a disturbance that causes
distortion in a current to a power converter, in association with a
phase angle of a voltage of an AC power supply. The power
conversion controller controls ON/OFF operations by using the
values stored in the storage to compensate for a manipulated
variable of control performed by the power converter in association
with the phase angle of the voltage of the AC power supply.
Inventors: |
Taniguchi; Tomoisa (Osaka,
JP), Sekimoto; Morimitsu (Osaka, JP),
Ogawa; Takurou (Osaka, JP), Tooyama; Eiji (Osaka,
JP), Hayashi; Nobuo (Osaka, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
DAIKIN INDUSTRIES, LTD. |
Osaka-shi, Osaka |
N/A |
JP |
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Assignee: |
DAIKIN INDUSTRIES, LTD.
(Osaka-Shi, JP)
|
Family
ID: |
54194741 |
Appl.
No.: |
15/123,564 |
Filed: |
March 27, 2015 |
PCT
Filed: |
March 27, 2015 |
PCT No.: |
PCT/JP2015/001800 |
371(c)(1),(2),(4) Date: |
September 02, 2016 |
PCT
Pub. No.: |
WO2015/146197 |
PCT
Pub. Date: |
October 01, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170077829 A1 |
Mar 16, 2017 |
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Foreign Application Priority Data
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|
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Mar 27, 2014 [JP] |
|
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2014-065520 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02P
29/50 (20160201); H02M 7/5395 (20130101); H02M
7/53873 (20130101); H02M 1/10 (20130101); H02M
1/12 (20130101); H02M 1/14 (20130101); H02P
23/26 (20160201); H02P 27/085 (20130101); H02M
5/458 (20130101); H02M 7/4826 (20130101); H02M
1/0022 (20210501); H02M 1/0025 (20210501); H02P
2205/00 (20130101) |
Current International
Class: |
H02M
5/458 (20060101); H02M 7/5387 (20070101); H02M
1/12 (20060101); H02M 1/10 (20060101); H02M
7/5395 (20060101); H02P 27/08 (20060101); H02P
23/26 (20160101); H02P 29/50 (20160101); H02M
1/14 (20060101); H02M 7/48 (20070101); H02M
1/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-51589 |
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Feb 2002 |
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JP |
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2005-124298 |
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May 2005 |
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JP |
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2005-130675 |
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May 2005 |
|
JP |
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2009-225631 |
|
Oct 2009 |
|
JP |
|
Other References
International Search Report issued in PCT/JP2015/001800, dated Jun.
30, 2015. cited by applicant .
Extended European Search Report dated Oct. 17, 2017 in Patent
Application No. 15767771.7. cited by applicant.
|
Primary Examiner: Zhang; Jue
Assistant Examiner: Dang; Trinh
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
The invention claimed is:
1. A power conversion device comprising: a power converter
configured to convert, by performing ON/OFF operations on a
plurality of switching elements, either an alternating current
output from an AC power supply or a direct current converted from
the alternating current into a different alternating current having
a predetermined frequency and a predetermined voltage; a capacitor
configured to smooth a ripple voltage generated as a result of the
ON/OFF operations; a storage configured to store multiple values,
each correlated to a disturbance that causes distortion in an input
current to the power converter, in association with a phase angle
of a voltage of the AC power supply; and a power conversion
controller configured to control the ON/OFF operations by using the
multiple values stored in the storage to compensate for a
manipulated variable of control performed by the power converter in
association with the phase angle of the voltage of the AC power
supply.
2. The power conversion device of claim 1, wherein each of the
multiple values correlated to the disturbance is selected from a
group consisting of: the input current to the power converter; an
output current value of a converter circuit configured to convert
an output of the AC power supply into a direct current; a voltage
of the capacitor; an energy of the capacitor; a deviation of the
input current to the power converter from a command value of the
input current to the power converter; a deviation of the output
current value of the converter circuit configured to convert the
output of the AC power supply into a direct current from a current
command specifying the output current value; a deviation of the
voltage of the capacitor from a command value of the voltage of the
capacitor; and a deviation of the energy of the capacitor from a
command value of the energy.
3. The power conversion device of claim 1, wherein the power
conversion controller controls a power of the power converter based
on the multiple values stored in the storage.
4. The power conversion device of claim 1, wherein the power
conversion controller controls a current at the power converter
based on the multiple values stored in the storage.
5. The power conversion device of claim 1, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
6. The power conversion device of claim 1, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
7. The power conversion device of claim 2, wherein the power
conversion controller controls a power of the power converter based
on the multiple values stored in the storage.
8. The power conversion device of claim 2, wherein the power
conversion controller controls a current at the power converter
based on the multiple values stored in the storage.
9. The power conversion device of claim 2, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
10. The power conversion device of claim 2, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
11. The power conversion device of claim 3, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
12. The power conversion device of claim 3, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
13. The power conversion device of claim 4, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
14. The power conversion device of claim 4, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
15. The power conversion device of claim 5, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
16. The power conversion device of claim 7, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
17. The power conversion device of claim 7, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
18. The power conversion device of claim 8, wherein the power
conversion controller compensates for the manipulated variable
using the multiple values correlated to the disturbance.
19. The power conversion device of claim 8, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
20. The power conversion device of claim 9, wherein if the multiple
values stored in the storage are discontinuous, the power
conversion controller makes interpolation between the discontinuous
values using data stored in the storage.
Description
TECHNICAL FIELD
The present invention relates to a power conversion device.
BACKGROUND ART
In air conditioners, for example, a power conversion device,
including a converter circuit and an inverter circuit, is used to
supply power to the motor of a compressor. Among such power
conversion devices, some exemplary power conversion device attempts
to increase the power factor by adopting a capacitor with a small
capacitance, which is on the order of one-hundredth of that of a
normal smoothing capacitor, as a capacitor provided between the
converter circuit and the inverter circuit (such a capacitor will
be hereinafter referred to as a "DC link capacitor"). Such a power
conversion device is disclosed, for example, in Patent Document
1.
CITATION LIST
Patent Document
PATENT DOCUMENT 1: Japanese Unexamined Patent Publication No.
2002-51589
SUMMARY OF INVENTION
Technical Problem
In such a power conversion device, a reactor is often provided on
an input side (i.e., AC side) or output side (i.e., DC side) of the
converter circuit. This reactor and the DC link capacitor together
form an LC resonant circuit, the resonance of which may cause
distortion in the output current or voltage waveform of the
converter circuit, i.e., may cause an increase in harmonics.
Likewise, even if there are no reactors, the inductance of a power
supply system and the capacitor in the power conversion device may
also form an LC resonant circuit, which may also cause distortion
in current waveform. That is to say, the deviation of a current
from a command value thereof increases.
Naturally, such harmonics need to be reduced, but it is not easy to
provide an appropriate countermeasure against them. Particularly,
the smaller the capacitance of the capacitor forming part of the LC
resonant circuit, the higher the LC resonant frequency, and the
more difficult it is to take an appropriate countermeasure.
In view of the foregoing background, it is therefore an object of
the present invention to reduce the deviation of a current from a
command value thereof in a power conversion device.
Solution to the Problem
To overcome this problem, a first aspect of the present invention
provides a power conversion device including:
a power converter (13) configured to convert, by performing ON/OFF
operations on a plurality of switching elements (Su, Sv, Sw, Sx,
Sy, Sz), either an alternating current output from an AC power
supply (30) or a direct current converted from the alternating
current into a different alternating current having a predetermined
frequency and a predetermined voltage;
a capacitor (12a) configured to smooth a ripple voltage generated
as a result of the ON/OFF operations;
a storage (62) configured to store multiple values, each correlated
to a disturbance that causes distortion in a current (Iin) to the
power converter (13), in association with a phase angle (.theta.in)
of a voltage (Vin) of the AC power supply (30); and
a power conversion controller (50, 60) configured to control the
ON/OFF operations by using the values stored in the storage (62) to
compensate for a manipulated variable (iT*) of control performed by
the power converter (13) in association with the phase angle
(.theta.in) of the voltage (Vin) of the AC power supply (30).
According to this configuration, the ON/OFF operations of the power
converter (13) are performed based on the values stored in the
storage (62).
A second aspect of the present invention is an embodiment of the
first aspect. In the second aspect, each of the values correlated
to the disturbance is selected from the group consisting of:
the current to the power converter (13);
an output current value (|Iin|) of a converter circuit (11)
configured to convert an output of the AC power supply (30) into a
direct current;
a voltage (vdc) of the capacitor (12a);
an energy (Ce) of the capacitor (12a);
a deviation of the current to the power converter (13) from a
command value of the current to the power converter (13);
a deviation of the output current value (|Iin|) of the converter
circuit (11) configured to convert the output of the AC power
supply (30) into the direct current from a current command (|Iin*|)
specifying the output current value (|Iin|);
a deviation of the voltage (vdc) of the capacitor (12a) from a
command value (vdc*) of the voltage (vdc) of the capacitor (12a);
and
a deviation of the energy (Ce) of the capacitor (12a) from a
command value (vdc*) of the energy (Ce).
A third aspect of the present invention is an embodiment of the
first or second aspect. In the third aspect,
the power conversion controller (50, 60) controls a power of the
power converter (13) based on the values stored in the storage
(62).
According to this configuration, the power of the power converter
(13) may be controlled based on the stored values.
A fourth aspect of the present invention is an embodiment of the
first or second aspect.
In the fourth aspect,
the power conversion controller (50, 60) controls a current at the
power converter (13) based on the values stored in the storage
(62).
According to this configuration, the current at the power converter
(13) may be controlled based on the stored values.
A fifth aspect of the present invention is an embodiment of any one
of the first to fourth aspects. In the fifth aspect,
the power conversion controller (50, 60) compensates for the
manipulated variable (iT*) using the multiple different values
correlated to the disturbance.
According to this configuration, the power or current of the power
converter (13) may be controlled based on the multiple stored
values.
A sixth aspect of the present invention is an embodiment of any one
of the first to fifth aspects. In the sixth aspect,
if the values stored in the storage (62) are discontinuous, the
power conversion controller (50, 60) makes interpolation between
the discontinuous values using data stored in the storage (62).
Advantages of the Invention
According to these various aspects described above, the deviation
of a current from a command value thereof may be reduced in a power
conversion device.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a configuration for a power conversion device
according to a first embodiment of the present invention.
FIG. 2 shows the respective waveforms of a current of an AC power
supply, a voltage of the AC power supply, and a DC link
voltage.
FIG. 3 illustrates a control system for an inverter circuit
according to the first embodiment.
FIG. 4 illustrates an exemplary configuration for a
compensator.
FIG. 5 shows how the compensator performs its compensation
operation.
FIG. 6 shows the respective waveforms of a supply voltage, a phase
angle, a current command value, an output current value, a
deviation, a second current command value, and a drive current
command value.
FIG. 7 illustrates a configuration for a compensator according to a
variation of the first embodiment.
FIG. 8 shows how to update a deviation storage in a situation where
one storage period is shorter than one carrier period.
FIG. 9 illustrates a control system for an inverter circuit
according to a second embodiment.
FIG. 10 illustrates a control system for an inverter circuit
according to a third embodiment.
FIG. 11 illustrates an exemplary configuration for a feedback
controller.
FIG. 12 illustrates a control system for an inverter circuit
according to a fourth embodiment.
FIG. 13 illustrates a control system for an inverter circuit
according to a fifth embodiment.
FIG. 14 is a flowchart showing how to update a deviation storage
according to a sixth embodiment.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention will now be described with
reference to the accompanying drawings. Note that the following
embodiments are only exemplary ones in nature, and are not intended
to limit the scope, application or uses of the present
invention.
<<First Embodiment of this Invention>>
FIG. 1 illustrates a configuration for a power conversion device
(10) according to a first embodiment of the present invention. This
power conversion device (10) may be used to supply power to a motor
for driving the compressor of an air conditioner (not shown), for
example, and other devices.
As shown in FIG. 1, the power conversion device (10) includes a
converter circuit (11), a DC section (12), an inverter circuit
(13), a controller (50), and a compensator (60). The power
conversion device (10) converts AC power supplied from a
single-phase AC power supply (30) into AC power having a
predetermined frequency and a predetermined voltage, and supplies
the converted AC power to a motor (20). The motor (20) is provided
to drive the compressor described above and may be a so-called
"interior permanent magnet (IPM) motor," for example.
<Converter Circuit>
The converter circuit (11) is connected to the AC power supply (30)
via a reactor (L1), and rectifies the alternating current supplied
from the AC power supply (30) into a direct current. In this
example, the converter circuit (11) is configured as a diode bridge
circuit in which four diodes (D1-D4) are connected together to form
a bridge. Using these diodes (D1-D4), the converter circuit (11)
subjects the AC voltage of the AC power supply (30) to a full-wave
rectification, thereby converting the AC voltage into a DC
voltage.
<DC Section>
The DC section (12) includes a capacitor (12a), which is connected
between the positive and negative output nodes of the converter
circuit (11). Thus, a DC voltage generated between the two
terminals of the capacitor (12a) (hereinafter referred to as a "DC
link voltage (vdc)") is applied to an input node of the inverter
circuit (13). If no reactor (L1) is provided closer to the AC power
supply than the converter circuit (11) is, then the capacitor (12a)
is connected to the positive output node of the converter circuit
(11) via another reactor (hereinafter referred to as a reactor
(L2)). The reactor (L1) and the capacitor (12a) form an LC resonant
circuit. Likewise, the reactor (L2) and the capacitor (12a) also
form an LC resonant circuit. Even if no reactors (L1, L2) were
provided, an LC resonant circuit would also be formed by an
inductance that the power supply system has and the capacitor
(12a). The LC resonance produced in this LC resonant circuit may
cause distortion in the output current waveform of the converter
circuit (11). Thus, in this embodiment, the compensator (60) to be
described in detail later provides a countermeasure against the
distortion of the output current waveform.
This capacitor (12a) has such a capacitance that allows itself to
smooth only a ripple voltage (voltage variation) generated while
the switching elements (to be described later) of the inverter
circuit (13) are performing a switching operation. That is to say,
the capacitor (12a) is a small-capacitance capacitor which does not
have such a capacitance that allows itself to smooth the voltage
rectified by the converter circuit (11) (i.e., a voltage varying
according to the supply voltage). A film capacitor may be used as
the capacitor (12a).
Since such a small-capacitance capacitor is adopted as the
capacitor (12a), the DC link voltage (vdc) pulsates at twice as
high a frequency as that of the supply voltage. FIG. 2 shows the
respective waveforms of the current of the AC power supply (30),
the voltage (Vin) of the AC power supply (30), and the DC link
voltage (vdc). In this example, the DC link voltage (vdc) has so
large a pulsation that its maximum value (Vmax) becomes twice or
more as large as its minimum value (Vmin).
<Inverter Circuit>
The inverter circuit (13) has its input node connected to the
capacitor (12a), and is supplied with a pulsating DC voltage (i.e.,
the DC link voltage (vdc)). By turning the switching elements (to
be described later) ON and OFF, the inverter circuit (13) converts
the output of the DC section (12) into three-phase alternating
currents (U, V, W), and supplies these currents to the motor (20).
That is to say, the motor (20) constitutes a load for the inverter
circuit (13).
The inverter circuit (13) of this embodiment has a configuration in
which each of a plurality of switching elements is
bridge-connected. This inverter circuit (13) includes six switching
elements (Su, Sv, Sw, Sx, Sy, Sz) in order to output three-phase
alternating currents to the motor (20). More specifically, this
inverter circuit (13) includes three switching legs in each of
which two switching elements are connected together in series. In
each switching leg, an intermediate point between the upper-arm
switching element (Su, Sv, Sw) and the lower-arm switching element
(Sx, Sy, Sz) is connected to the coil of an associated phase of the
motor (20). Also, a freewheeling diode (Du, Dv, Dw, Dx, Dy, Dz) is
connected anti-parallel to each of these switching elements (Su,
Sv, Sw, Sx, Sy, Sz).
By turning these switching elements (Su, Sv, Sw, Sx, Sy, Sz) ON and
OFF, the inverter circuit (13) switches the DC link voltage (vdc)
supplied from the DC section (12) and converts the DC link voltage
(vdc) into a three-phase AC voltage having a predetermined
frequency and a predetermined voltage, and supplies the voltage to
the motor (20). Such control of the ON/OFF operations is performed
by the controller (50). That is to say, the inverter circuit (13)
converts the direct current, into which the alternating current
supplied from the AC power supply (30) has been converted, into an
alternating current having a predetermined frequency and a
predetermined voltage, and functions as an exemplary power
converter according to the present invention.
<Controller>
FIG. 3 illustrates a control system for the inverter circuit (13)
according to the first embodiment. This controller (50) includes a
microcomputer (not shown) and a program installed therein to
operate the microcomputer. By controlling the ON/OFF operations of
the switching elements (Su, Sv, Sw, Sx, Sy, Sz), the controller
(50) controls the current of the inverter circuit (13). That is to
say, as the output of the inverter circuit (13) is controlled by
the controller (50), the drive of the motor (20) is controlled. The
drive of the motor (20) may be controlled, for example, by d-q axis
vector control. The controller (50) of this embodiment includes a
velocity controller (51), a multiplier (52), an adder (53), a dq
current command value generator (54), a coordinate transformer
(55), a dq axis current controller (56), and a PWM calculator
(57).
The velocity controller (51) calculates the deviation of the
rotational angular frequency (.omega.) of the mechanical angle of
the motor (20) from the command value (.omega.*) of the mechanical
angle. Then, the velocity controller (51) performs proportional
integral (PI) operation on the deviation and outputs a result of
the operation as a first current command value (im*) to the
multiplier (52).
The multiplier (52) multiplies together the absolute value of the
sine value (|sin(.theta.in)|) of the phase angle (.theta.in) of the
voltage (Vin) at the AC power supply (30) and the first current
command value (im*), and outputs a result of the multiplication as
a second current command value (iT*). This second current command
value (iT*) is a motor current amplitude command value, and is an
exemplary manipulated variable of the control to be performed by
the power converter in accordance with the present invention.
The adder (53) adds together the second current command value (iT*)
and a compensation current command value (icomp*) (to be described
later) generated by the compensator (60), and outputs a result of
the addition (hereinafter referred to as a "drive current command
value (idq*)") to the dq current command value generator (54).
The dq current command value generator (54) calculates a d-axis
current command value (id*) and a q-axis current command value
(iq*) based on the drive current command value (idq*) and the
command value (.beta.*) of the phase (.beta.) of the current to
flow through the motor (20), and outputs them to the dq axis
current controller (56). Specifically, the dq current command value
generator (54) generates a d-axis current command value (id*) by
multiplying the sine value (-sin .beta.*) of the command value
(.beta.*) and the drive current command value (idq*) together, and
also generates a q-axis current command value (iq*) by multiplying
the cosine value (cos .beta.*) of the command value (.beta.*) and
the drive current command value (idq*) together.
The coordinate transformer (55) calculates a d-axis current value
(id) and a q-axis current value (iq) based on the angle of rotation
(which is an electrical angle (.theta.e)) of the rotor (not shown)
of the motor (20) and phase currents (iu, iv, iw) of the inverter
circuit (13).
The dq axis current controller (56) generates a d-axis voltage
command value (Vd*) and a q-axis voltage command value (Vq*) so as
to reduce the deviation of the d-axis current value (id) from the
d-axis current command value (id*) and the deviation of the q-axis
current value (iq) from the q-axis current command value (iq*),
respectively, and outputs these voltage command values to the PWM
calculator (57).
The PWM calculator (57) receives the d-axis and q-axis voltage
command values (Vd*, Vq*), the DC link voltage (vdc), and the
electrical angle (.theta.e). Based on these values, the PWM
calculator (57) generates a control signal (G) (hereinafter also
referred to as a "PWM output") to control the ON/OFF operations of
the respective switching elements (Su, Sv, Sw, Sx, Sy, Sz) of the
inverter circuit (13) and outputs the control signal (G) to the
inverter circuit (13). The PWM output (G) is updated on a
predetermined period (hereinafter referred to as a "carrier period
(Tc)" or an update period (Tc)") basis.
<Compensator>
The compensator (60) generates a compensation current command value
(icomp*) to compensate for (as will be described later) the second
current command value (iT*). In this example, the controller (50)
and the compensator (60) together form an exemplary power
conversion controller according to the present invention. The
compensator (60) includes a microcomputer (not shown) and a program
installed therein to operate the microcomputer. FIG. 4 shows an
exemplary configuration for the compensator (60). As shown in FIG.
4, this compensator (60) includes a subtractor (61), a deviation
storage (62), a first index generator (63), a power supply phase
calculator (64), a second index generator (65), and a magnitude of
compensation calculator (66).
--Subtractor (61)--
The subtractor (61) calculates the deviation of the output current
value (|Iin|) of the converter circuit (11) from a current command
(|Iin*|) specifying the output current value (|Iin|). This
deviation is correlated to a disturbance that causes distortion in
a current to the inverter circuit (13) (i.e., the output current
value (|Iin|)). That is to say, this deviation is an exemplary
value correlated to a disturbance that causes distortion in a
current (Iin) to the power converter. Note that the current value
(|Iin|) is a measured value. Also, the current command (|Iin*|) is
generated as the product of the amplitude of the fundamental wave
component of the input current value (Iin) of the converter circuit
(11) and | sin(.theta.in)|.
--Deviation Storage (62)--
The deviation storage (62) has a plurality (or an arrangement) of
storage areas and stores the deviations calculated by the
subtractor (61). This deviation storage (62) is an exemplary
storage according to the present invention. The number (hereinafter
referred to as "K") of the storage areas in the deviation storage
(62) is set such that a period (hereinafter referred to as a
storage period (Tm)) corresponding to .pi./K [rad] of one voltage
period of the AC power supply (30) (hereinafter referred to as a
"power supply period") becomes equal to or shorter than one carrier
period (Tc). If K is set as described above, the deviation storage
(62) is allowed to store K deviations in a period corresponding to
a half of one power supply period (hereinafter referred to as a
"power supply half period"). In this embodiment, one storage period
(Tm) agrees with one carrier period (Tc).
--First Index Generator (63)--
The first index generator (63) calculates an index (idx) specifying
any of the storage areas of the deviation storage (62) based on the
phase angle (.theta.in)=.theta.in1 when the control processing
(such as current control) is started. In this example,
idx=.theta.in1/(.pi./K) is supposed to be satisfied. Thus, the
index (idx) falls within the range of 0 to K-1.
In the deviation storage (62), the deviation at the phase angle
(.theta.in1) is stored in a storage area associated with the index
(idx) calculated. That is to say, the deviation storage (62) stores
multiple deviations of the output current values (|Iin|) from the
current command (|Iin*|) in association with the phase angle
(.theta.in) of the voltage (Vin) of the AC power supply (30). Since
the index (idx) and the phase angles (.theta.in) are associated
with each other as described above, multiple values (i.e.,
deviations) correlated to the disturbance to the intervals of the
storage periods (Tm) are stored side by side in the deviation
storage (62).
--Power Supply Phase Calculator (64)--
The power supply phase calculator (64) calculates the phase angle
(.theta.in2) at the timing of compensating for the second current
command value (iT*). In this example, the power supply phase
calculator (64) outputs, based on the phase angle (.theta.in1) at
the starting point of control processing (such as current control),
the phase angle (.theta.in2) at the endpoint of an update period
(Tc) to which the output of the control processing is applied as a
PWM signal.
--Second Index Generator (65)--
The second index generator (65) calculates, based on the phase
angle (.theta.in)=.theta.in2 obtained by the power supply phase
calculator (64), an index (idx) specifying any of the storage areas
of the deviation storage (62). The index (idx) may be calculated in
the same way as in the first index generator (63), and
idx=.theta.in2/(.pi./K) is supposed to be satisfied.
--Magnitude of Compensation Calculator (66)--
The magnitude of compensation calculator (66) calculates a
compensation current command value (icomp*). Specifically, using
the index (idx) calculated by the second index generator (65), the
magnitude of compensation calculator (66) retrieves a deviation
from any of the storage areas of the deviation storage (62). In the
following description, the deviation retrieved will be identified
herein by Iin_err. Then, the magnitude of compensation calculator
(66) calculates the compensation current command value (icomp*) by
icomp*=Gp.times.Iin_err, where Gp is a gain which may be determined
appropriately by experiments, for example. The compensation current
command value (icomp*) thus calculated is output to the adder (53)
of the controller (50). In this embodiment, the magnitude of
compensation calculator (66) and the adder (53) together form a
current command compensator.
<How Power Conversion Device Operates>
FIG. 5 shows how the compensator (60) performs its compensation
operation. In FIG. 5, shown are m.sup.th through (m+2).sup.th
carrier periods (Tc), where m is an integer equal to or greater
than zero. Meanwhile, FIG. 6 shows the respective waveforms of a
supply voltage (Vin), a phase angle (.theta.in), a current command
(|Iin*|), an output current value (|Iin|), a deviation (Iin_err), a
second current command value (iT*), and a drive current command
value (idq*). In FIG. 6, shown are the waveforms in three power
supply half periods (i.e., from (n-1).sup.th through (n+1).sup.th
power supply half periods).
When a carrier period (Tc) begins, the controller (50) starts
performing the control processing. For example, when the control
processing for the m.sup.th carrier period (Tc) starts, the
controller (50) measures the output current value (|Iin|) and the
phase angle (.theta.in). Then, in the controller (50), the velocity
controller (51) generates a first current command value (im*) based
on the deviation of the rotational angular frequency (.omega.) from
a command value (.omega.*) thereof. The first current command value
(im*) is modulated by the multiplier (52) and then output as the
second current command value (iT*).
Meanwhile, in the compensator (60), the second index generator (65)
calculates an index (idx) based on the phase angle (.theta.in1)
detected. In this case, the value calculated is supposed to be
idx=j2. Then, the magnitude of compensation calculator (66)
retrieves a deviation (hereinafter identified by Iin_err(j2))
associated with the index (idx)=j2 thus calculated from the
deviation storage (62). The magnitude of compensation calculator
(66) calculates the compensation current command value (icomp*)
using the deviation Iin_err(j2) thus retrieved.
This compensation current command value (icomp*) is added by the
adder (53) to (and compensates for) the second current command
value (iT*). In this manner, the second current command value (iT*)
is compensated for such that the distortion caused in the output
current (Iin) due to the deviation (correlated to the disturbance)
of the output current value (|Iin|) from the current command
(|Iin*|) is reduced. The second current command value (iT*) thus
corrected is output as a drive current command value (idq*) to the
dq current command value generator (54).
In this case, the deviation (Iin_err) used to calculate the
compensation current command value (icomp*) is that of a power
supply half period (n-1) preceding the present power supply half
period (n). That is to say, the second current command value (iT*)
in the phase corresponding to the index (idx)=j2 of the n.sup.th
power supply half period is compensated for based on the deviation
Tin err(j2) stored in the phase corresponding to the index (idx)=j2
of the (n-1).sup.th power supply half period (see FIG. 6). In FIG.
6, a situation where gain (Gp)=1is illustrated as an example.
As can be seen, in the controller (50), the dq current command
value generator (54) generates a d-axis current command value (id*)
and a q-axis current command value (iq*) using the drive current
command value (idq*) that is the compensated second current command
value (iT*). Then, the dq axis current controller (56) generates a
d-axis voltage command value (Vd*) and a q-axis voltage command
value (Vq*). When the d-axis voltage command value (Vd*) and q-axis
voltage command value (Vq*) are generated, the PWM calculator (57)
outputs a control signal (G) to the inverter circuit (13). In
response, the inverter circuit (13) operates so as to reduce the
distortion of the output current waveform of the converter circuit
(11). The LC resonance produced by the capacitor (12a) and the
reactors (L1, L2) may be reduced in this manner based on the stored
deviation (i.e., a value correlated to the disturbance), because
the LC resonance has a steady-state repetitive waveform.
Meanwhile, in the compensator (60), the deviation storage (62)
updates, based on a disturbance detected every carrier period (Tc),
the storage area to store the disturbance. For example, in the
m.sup.th carrier period (Tc), when finishing outputting the
compensation current command value (icomp*), the compensator (60)
updates the data stored in the deviation storage (62) based on the
output current value (|Iin|) and phase angle (.theta.in1) which
were detected when the m.sup.th carrier period (Tc) began.
Specifically, the first index generator (63) calculates an index
based on the phase angle (.theta.in1). In this example, idx=j1. As
a result, in the compensator (60), the j1.sup.th deviation
Iin_err(j1) is updated.
The same operation is performed in the (m+1).sup.th carrier period
(Tc) as well. In the (m+1).sup.th carrier period (Tc), idx=j1+1 is
satisfied, because the storage period (Tm) agrees with the carrier
period (Tc). In the (m+1).sup.th carrier period (Tc), supposing the
present power supply half period is the n.sup.th one, the second
current command value (iT*) in a phase corresponding to the index
(idx)=j2+1 of the n.sup.th power supply half period is compensated
for based on the deviation Iin_err(j2+1) stored in the phase
corresponding to the index (idx)=j2+1 of the (n-1).sup.th power
supply half period. Also, in the (m+1).sup.th carrier period (Tc),
the (j2+1).sup.th deviation Iin_err(j2+1) is updated.
In the embodiment described above, the index (idx) is calculated
based on the phase angle (.theta.in) when the control processing is
started in each carrier period (Tc). The output current value
(|Iin|) is also detected at the starting point of the control
processing. If the carrier period (Tc) agrees with the storage
period (Tm) as in this embodiment, the index (idx) is updated
synchronously with the start of the control processing, and the
index increments one by one every control period. Thus, every data
in the deviation storage (62) is updated without exception every
power supply half period.
<Advantages of This Embodiment>
According to the embodiment described above, deviations (i.e.,
values correlated to a disturbance) are stored, and the manipulated
variable (iT*) of current control of the inverter circuit (13) is
compensated for based on the value stored a power supply half
period ago. Thus, according to this embodiment, the deviation of a
current from a command value thereof may be reduced. More
specifically, the distortion of the output current of the converter
circuit (11) (i.e., the distortion of an input current to the
inverter circuit (13)) caused by a disturbance with a repetitive
waveform such as LC resonance may be reduced easily. In addition,
the smaller the capacitance of the capacitor forming part of an LC
resonant circuit is, the more effectively this method is
applicable. The smaller the capacitance of the capacitor forming
part of an LC resonance circuit, the higher the frequency of the LC
resonance circuit, and the more speedily the compensation operation
needs to be done. According to this embodiment, the compensated
value is obtained based on the stored deviations, and therefore,
the compensation may be done speedily.
<<Variation of First Embodiment>>
An example in which one storage period (Tm) is set to be shorter
than one carrier period (Tc) will be described as a variation of
the first embodiment. FIG. 7 illustrates a configuration for a
compensator (60) according to such a variation of the first
embodiment. As shown in FIG. 7, the compensator (60) of this
variation includes not only all components of the compensator (60)
of the first embodiment but also an additional data interpolator
(68) as well.
FIG. 8 shows how to update the deviation storage (62) in a
situation where one storage period (Tm) is shorter than one carrier
period (Tc). In FIG. 8, shown are m.sup.th and (m+1).sup.th carrier
periods (Tc), where m is an integer equal to or greater than zero.
As shown in FIG. 8, if one storage period (Tm) is shorter than one
carrier period (Tc), the index (idx) is updated asynchronously with
the start of the control processing.
Thus, in two consecutive carrier periods (Tc), the index (idx) may
increase by two. In the example shown in FIG. 8, the index (idx)
when the m.sup.th carrier period (Tc) begins is j1, and the index
(idx) when the (m+1).sup.th carrier period (Tc) begins is j1+2.
Supposing a disturbance detected every carrier period (Tc) is used
to update the storage areas, if the index (idx) has increased by
two in this manner, then the data stored in the storage area
associated with the index (idx)=j1+1 will not be updated. That is
to say, unless the storage areas of the deviation storage (62) are
updated sequentially and continuously from the top, there may be
some non-updated storage areas left in some cases. Thus, in this
variation, the data interpolator (68) is made to sense that the
index has increased by two or more and to make interpolation
between the data in the non-updated storage areas using the
deviations obtained last time and the deviations obtained this
time.
In the example shown in FIG. 8, in the m.sup.th carrier period
(Tc), the storage area (idx=j1) to store the disturbance detected
in this carrier period (Tc) is updated. Next, when the control
processing for the (m+1).sup.th carrier period (Tc) is started, the
first index generator (63) calculates the index (idx)=j1+2. Then,
the deviation Iin_err(j1+2) is stored in the storage area
associated with that index (idx)=j1+2 (see FIG. 8).
Subsequently, the data interpolator (68) compares the present index
(idx)=j1+2 to the index (idx)=j1 that has been calculated in the
previous carrier period (Tc), i.e., the m.sup.th carrier period
(Tc). It can be seen that since the index (idx) has increased in
this example by two from that of the previous carrier period (Tc),
the data associated with the index (idx)=j1 +1 has not been
updated. Thus, the data interpolator (68) generates data associated
with the index (idx)=j1+1 by making interpolation between the data
associated with the index (idx) =j1 and the data associated with
the index (idx)=j1+2, and stores the data thus generated in the
deviation storage (62). As can be seen, according to this
variation, if the values stored in the storage (62) are
discontinuous (i.e., if there is any storage area in which the data
has not been updated), that discontinuous interval (i.e., the
storage area in which the data has not been updated) is
interpolated based on the data stored in the storage (62).
According to this variation, such interpolation processing may
prevent the deviation storage (62) from having any storage area
which is not updated for a long time. That is to say, according to
this variation, even if the storage period (Tm) is asynchronous
with the carrier period (Tc), the distortion of the output current
of the converter circuit (11) may still be reduced with more
reliability. In other words, the deviation of a current from a
command value thereof may also be reduced according to this
variation.
Note that even if the index (idx) increases by three or more in two
consecutive carrier periods (Tc), the data stored in a non-updated
storage area may also be updated in the same way as described above
based on the data stored in an updated storage area.
<<Second Embodiment of This Invention>>
FIG. 9 illustrates a control system for an inverter circuit (13)
according to a second embodiment. In this embodiment, another
compensator (60) and a subtractor (67) are added as shown in FIG. 9
to the control system of the first embodiment. The additional
compensator (60) also has the same configuration as the compensator
(60) of the first embodiment. However, a different signal is input
to the additional compensator (60) from the one input to the
compensator (60) of the first embodiment. In FIG. 9, these two
compensators (60) are respectively identified by reference signs
with two different branch numbers (-1, -2). In this example, the
original compensator is identified by (60-1) and the additional
compensator is identified by (60-2).
In the additional compensator (60-2), the subtractor (61)
calculates the deviation of capacitor energy (Ce) from a command
value (Ce*) of the capacitor energy (Ce). Specifically, the
subtractor (61) subtracts the capacitor energy (Ce) from the
command value (Ce*) and outputs the difference thus obtained as the
deviation. In this case, the capacitor energy (Ce) is energy stored
in the capacitor (12a) of the DC section (12). This value may be
calculated based on the DC link voltage (vdc). Also, the command
value (Ce*) is its command value and calculated based on a target
value of the DC link voltage (vdc). The target value of the DC link
voltage (vdc) is defined such that the DC link voltage (vdc) has a
substantially sinusoidal waveform.
In the deviation storage (62) of the additional compensator (60-2),
the deviation of the capacitor energy (Ce) from the command value
(Ce*) thereof is stored in association with the phase angle
(.theta.in) of the voltage (Vin) of the AC power supply (30). This
deviation is also an exemplary value correlated to a disturbance
that causes distortion in the current (Iin) to the power converter
according to the present invention.
Then, the compensation current command value (icomp**) obtained by
the additional compensator (60-2) is subtracted by the subtractor
(67) from the output of the original compensator (60-1). The output
of the subtractor (67) is supplied as a compensated value of the
second current command value (iT*) to the adder (53). In this
example, these two compensators (60-1, 60-2) and the adder (53)
together form a current command value compensator.
With such a configuration adopted, according to this embodiment,
the compensation is made based on not only the output current value
(|Iin|) of the converter circuit (11) but also the capacitor energy
(Ce) stored in the capacitor (12a) of the DC section (12). Such
additional compensation based on the capacitor energy (Ce) may
reduce the disturbance to be caused by input and output currents of
the capacitor (12a) in the DC section, and may bring the output
current value (|Iin|) of the converter circuit (11) even closer to
the current command (|Iin*|).
Specifically, according to this embodiment, if the capacitor energy
(Ce) of the DC section (12) is greater than the command value (Ce*)
of the capacitor energy, the second current command value (iT*) is
compensated for such that the output power of the inverter circuit
(13) is further increased. On the other hand, if the capacitor
energy (Ce) is less than the command value (Ce*), the second
current command value (iT*) is compensated for such that the output
power of the inverter circuit (13) is further decreased.
As can be seen from the foregoing description, according to this
embodiment, the compensated value is obtained based on the stored
deviations (i.e., values correlated to a disturbance), and
therefore, the compensation may be done speedily.
<<Third Embodiment of This Invention>>
FIG. 10 illustrates a control system for an inverter circuit (13)
according to a third embodiment. In this example, a feedback
controller (80) is added to the control system of the first
embodiment. The feedback controller (80) compensates for the
current command (|Iin*|) by performing feedback control such that
the deviation of the output current value (|Iin|) from the current
command (|Iin*|) decreases.
FIG. 11 illustrates an exemplary configuration for the feedback
controller (80). As shown in FIG. 11, the feedback controller (80)
includes a subtractor (81) and a PI calculator (82). The subtractor
(81) calculates the deviation of the output current value (|Iin|)
from a current command (|Iin*|) thereof. The PI calculator (82)
performs a proportional integral (PI) operation on the output of
the subtractor (81) and outputs a result of the operation as a
compensation current command value (icomp***), which is then added
to the output of the compensator (60). The sum is input to the
adder (53) of the controller (50).
With this feedback controller (80) provided, the distortion caused
in the output current of the converter circuit (11) due to not only
a steady-state disturbance such as the LC resonance mentioned above
but also a non-steady-state disturbance may be reduced. Note that
appropriate adjustment of the balance between the gain (Gp) of the
compensator (60) and the gain of the feedback controller (80) may
prevent the control by the feedback controller (80) from affecting
the control by the compensator (60) excessively.
<<Fourth Embodiment of This Invention>>
FIG. 12 illustrates a control system for an inverter circuit (13)
according to a fourth embodiment. The controller (50) of this
embodiment includes a velocity controller (51), a multiplier (52),
an adder (53), a coordinate transformer (55), a power controller
(58), a dq axis current controller (56), and a PWM calculator
(57).
The velocity controller (51) calculates the deviation of the
rotational angular frequency (.omega.) of the mechanical angle of
the motor (20) from a command value (.omega.*) of the mechanical
angle. Then, the velocity controller (51) performs proportional
integral (PI) operation on the deviation and outputs a result of
the operation as a first power command value (p*) to the multiplier
(52).
The multiplier (52) multiplies together the square of the sine
value (sin.sup.2(.theta.in)) of the phase angle (.theta.in) of the
voltage (Vin) at the AC power supply (30) and the first power
command value (p*), and outputs a result of the multiplication as a
second power command value (p**). This second power command value
(p**) is a command value of the power output from the inverter
circuit (13) (i.e., power converter), and is an exemplary
manipulated variable of the control to be performed by the power
converter.
The adder (53) adds together the second power command value (p**)
and a compensation power command value (pcomp*) (to be described
later) generated by the compensator (60), and outputs a result of
the addition (hereinafter referred to as a "drive power command
value (p***)") to the power controller (58).
The power controller (58) calculates, based on the drive power
command value (p***) and the number of revolutions (.omega.) of the
motor, a motor torque command value, generates a d-axis current
command value and a q-axis current command value in accordance with
the motor torque command value, and then outputs them to the
dq-axis current controller (56). Specifically, based on various
motor constants such as a d-axis inductance, a q-axis inductance,
the number of flux linkages, the coil resistance, and the number of
motor poles, the power controller (58) generates a d-axis current
command value and a q-axis current command value in accordance with
the motor torque command value.
The coordinate transformer (55) calculates a d-axis current value
(id) and a q-axis current value (iq) based on the angle of rotation
(which is an electrical angle (.theta.e)) of the rotor (not shown)
of the motor (20) and phase currents (iu, iv, iw) of the inverter
circuit (13).
The dq axis current controller (56) generates a d-axis voltage
command value (Vd*) and a q-axis voltage command value (Vq*) so as
to reduce the deviation of the d-axis current value (id) from the
d-axis current command value (id*) and the deviation of the q-axis
current value (iq) from the q-axis current command value (iq*),
respectively, and outputs these voltage command values to the PWM
calculator (57).
The PWM calculator (57) receives the d-axis and q-axis voltage
command values (Vd*, Vq*), the DC link voltage (vdc), and the
electrical angle (.theta.e). Based on these values, the PWM
calculator (57) generates a control signal (G) (hereinafter also
referred to as a "PWM output") to control the ON/OFF operations of
the respective switching elements (Su, Sv, Sw, Sx, Sy, Sz) of the
inverter circuit (13) and outputs the control signal (G) to the
inverter circuit (13). The PWM output (G) is updated on a
predetermined period (hereinafter referred to as a "carrier period
(Tc)" or an "update period (Tc)") basis.
<Compensator>
The compensator (60) generates a compensation power command value
(pcomp*) to compensate for (as will be described later) the second
power command value (p**). The compensator (60) includes a
microcomputer (not shown) and a program installed therein to
operate the microcomputer. As in the example shown in FIG. 4, the
compensator (60) of this embodiment also includes a subtractor
(61), a deviation storage (62), a first index generator (63), a
power supply phase calculator (64), a second index generator (65),
and a magnitude of compensation calculator (66).
--Subtractor (61)--
The subtractor (61) calculates the deviation of the output current
value (|Iin|) of the converter circuit (11) from a current command
(|Iin*|) specifying the output current value (|Iin|). This
deviation is an exemplary value correlated to a disturbance that
causes distortion in a current (Iin) to the power converter
according to the present invention. Note that the current value
(|Iin|) is a measured value. Also, the current command (|Iin*|) is
generated as the product of the amplitude of the fundamental wave
component of the input current value (Iin) of the converter circuit
(11) and |sin(.theta.in)|.
--Deviation Storage (62)--
The deviation storage (62) has a plurality (or an arrangement) of
storage areas and stores the deviations calculated by the
subtractor (61). This deviation storage (62) is an exemplary
storage according to the present invention. The number (hereinafter
referred to as "K") of the storage areas of the deviation storage
(62) is set such that a period (hereinafter referred to as a
storage period (Tm)) corresponding to .pi./K [rad] of one voltage
period of the AC power supply (30) (hereinafter referred to as a
"power supply period") becomes equal to or shorter than one carrier
period (Tc). If K is set as described above, the deviation storage
(62) is allowed to store K deviations in a period corresponding to
a half of one power supply period (hereinafter referred to as a
"power supply half period"). In this embodiment, one storage period
(Tm) agrees with one carrier period (Tc).
--First Index Generator (63)--
The first index generator (63) calculates an index (idx) specifying
any of the storage areas of the deviation storage (62) based on the
phase angle (.theta.in)=.theta.in1 when the control processing
(such current control) is started. In this example,
idx=.theta.in1/(.pi./K) is supposed to be satisfied. Thus, the
index (idx) falls within the range of 0 to K-1.
In the deviation storage (62), the deviation at the phase angle
(.theta.in1) is stored in a storage area associated with the index
(idx) calculated. That is to say, the deviation storage (62) stores
multiple deviations of the output current values (|Iin|) from the
current command (|Iin*|) thereof in association with the phase
angle (.theta.in) of the voltage (Vin) of the AC power supply (30).
Since the index (idx) and the phase angles (.theta.in) are
associated with each other as described above, multiple values
(i.e., deviations) correlated to the disturbance to the intervals
of the storage periods (Tm) are stored side by side in the
deviation storage (62).
--Power Supply Phase Calculator (64)--
The power supply phase calculator (64) calculates the phase angle
(.theta.in2) at the timing of compensating for the second current
command value (iT*). In this example, the power supply phase
calculator (64) outputs, based on the phase angle (.theta.in1) at
the starting point of control processing (such as current control),
the phase angle (.theta.in2) at the endpoint of an update period
(Tc) to which the output of the control processing is applied as a
PWM signal.
--Second Index Generator (65)--
The second index generator (65) calculates, based on the phase
angle (.theta.in2) obtained by the power supply phase calculator
(64), an index (idx) specifying any of the storage areas of the
deviation storage (62). The index (idx) may be calculated in the
same way as in the first index generator (63), and
idx=.theta.in1/(.pi./K) is supposed to be satisfied.
--Magnitude of Compensation Calculator (66)--
The magnitude of compensation calculator (66) calculates a
compensation power command value (pcomp*). Specifically, using the
index (idx) calculated by the second index generator (65), the
magnitude of compensation calculator (66) retrieves a deviation
from any of the storage areas of the deviation storage (62). In the
following description, the deviation retrieved will be identified
herein by Iin_err. Then, the magnitude of compensation calculator
(66) calculates the compensation power command value (pcomp*) by
pcomp*=--|Vinsin(.theta.in2)|.times.Iin_err. The compensation power
command value (pcomp*) thus calculated is output to the adder (53)
of the controller (50).
<How Power Conversion Device Operates>
Next, it will be described with reference to FIG. 5 how the power
conversion device of this embodiment operates. In FIG. 5, shown are
m.sup.th through (m+2).sup.th carrier periods (Tc), where m is an
integer equal to or greater than zero.
When a carrier period (Tc) begins, the controller (50) starts
performing the control processing. For example, when the control
processing for the m.sup.th carrier period (Tc) starts, the
controller (50) measures the output current value (|Iin|) and the
phase angle (.theta.in1). Then, in the controller (50), the
velocity controller (51) generates a first power command value (p*)
based on the deviation of the rotational angular frequency
(.omega.) from a command value (.omega.*) thereof. The first power
command value (p*) is modulated by being multiplied by
sin.sup.2(.theta.in) by the multiplier (52), and then is output as
the second power command value (p**).
Meanwhile, in the compensator (60), the second index generator (65)
calculates an index (idx) based on the phase angle (.theta.in1)
detected. In this case, the value calculated is supposed to be
idx=j2. Then, the magnitude of compensation calculator (66)
retrieves a deviation (hereinafter identified by Iin_err(j2))
associated with the index (idx)=j2 thus calculated from the
deviation storage (62). The magnitude of compensation calculator
(66) calculates the compensation power command value (pcomp*) using
the deviation Iin_err(j2) thus retrieved.
This compensation power command value (pcomp*) is added by the
adder (53) to (and compensates for) the second power command value
(p**). In this manner, the second power command value (p**) is
compensated for such that the distortion caused in the output
current (Iin) due to the deviation (correlated to the disturbance)
of the output current value (|Iin|) from the current command
(|Iin*|) is reduced. The second power command value (p**) thus
corrected is output as a drive power command value (p***) to the
power controller (58).
In this case, the deviation (Iin_err) used to calculate the
compensation power command value (pcomp*) is that of a power supply
half period (n-1) preceding the present power supply half period
(n). That is to say, the second power command value (p**) in the
phase corresponding to the index (idx)=j2 of the n.sup.th power
supply half period is compensated for based on the deviation
Iin_err(j2) stored in the phase corresponding to the index (idx)=j2
of the (n-1).sup.th power supply half period.
As can be seen, in the controller (50), a d-axis current command
value (id*) and a q-axis current command value (iq*) are generated
based on the drive power command value (p***) that is the
compensated second power command value (p**). Then, the dq axis
current controller (56) generates a d-axis voltage command value
(Vd*) and a q-axis voltage command value (Vq*). When the d-axis
voltage command value (Vd*) and q-axis voltage command value (Vq*)
are generated, the PWM calculator (57) outputs a control signal (G)
to the inverter circuit (13). In response, the inverter circuit
(13) operates so as to reduce the distortion of the output current
waveform of the converter circuit (11). The LC resonance produced
by the capacitor (12a) and the reactors (L1, L2) may be reduced in
this manner based on the stored deviation (i.e., a value correlated
to the disturbance), because the LC resonance has a steady-state
repetitive waveform.
Meanwhile, in the compensator (60), the deviation storage (62)
updates, based on a disturbance detected every carrier period (Tc),
the storage area to store the disturbance. For example, in the
m.sup.th carrier period (Tc), when finishing outputting the
compensation power command value (pcomp*), the compensator (60)
updates the data stored in the deviation storage (62) based on the
output current value (|Iin|) and phase angle (.theta.in1) which
were detected when the m.sup.th carrier period (Tc) began.
Specifically, the first index generator (63) calculates an index
based on the phase angle (.theta.in1). In this example, idx=j1. As
a result, in the compensator (60), the j1.sup.th deviation
Iin_err(j1) is updated.
The same operation is performed in the (m+1).sup.th carrier period
(Tc) as well. In the (m+1).sup.th carrier period (Tc), idx=j1+1 is
satisfied, because the storage period (Tm) agrees with the carrier
period (Tc). In the (m+1).sup.th carrier period (Tc), supposing the
present power supply half period is the n.sup.th one, the second
current command value (iT*) in a phase corresponding to the index
(idx)=j2+1 of the n.sup.th power supply half period is compensated
for based on the deviation Iin_err(j2+1) stored in the phase
corresponding to the index (idx)=j2+1 of the (n-1).sup.th power
supply half period. Also, in the (m+1).sup.th carrier period (Tc),
the (j2+1).sup.th deviation Iin_err(j2+1) is updated.
In the embodiment described above, the index (idx) is calculated
based on the phase angle (.theta.in) when the control processing is
started in each carrier period (Tc). The output current value
(|Iin|) is also detected at the starting point of the control
processing. If the carrier period (Tc) agrees with the storage
period (Tm) as in this embodiment, the index (idx) is updated
synchronously with the start of the control processing, and the
index increments one by one every control period. Thus, every data
in the deviation storage (62) is updated without exception every
power supply half period.
<Advantages of This Embodiment>
According to this embodiment, the manipulated variable of the power
control performed by the inverter circuit (13) is compensated for.
Even so, the same or similar advantages to those of the first
embodiment described above may also be achieved.
<<Fifth Embodiment of This Invention>>
FIG. 13 illustrates a control system for an inverter circuit (13)
according to a fifth embodiment. In this embodiment, another
compensator (60) and a subtractor (67) are added to the control
system of the first embodiment. The additional compensator (60)
also has the same configuration as the compensator (60) of the
first embodiment. However, a different signal is input to the
additional compensator (60) from the one input to the compensator
(60) of the first embodiment. In FIG. 13, these two compensators
(60) are respectively identified by reference signs with two
different branch numbers (-1, -2). In this example, the original
compensator is identified by (60-1) and the additional compensator
is identified by (60-2).
In the additional compensator (60-2), the subtractor (61)
calculates the deviation of the DC link voltage (vdc) from a
command value (vdc*) of the DC link voltage (vdc). Specifically,
the subtractor (61) subtracts the DC link voltage from the command
value (vdc*) and outputs the difference thus obtained as the
deviation.
In the deviation storage (62) of the additional compensator (60-2),
the deviation of the DC link voltage (vdc) from the command value
(vdc*) thereof is stored in association with the phase angle
(.theta.in) of the voltage (Vin) of the AC power supply (30). This
deviation is also an exemplary value correlated to a disturbance
that causes distortion in the current (Iin) to the power converter
according to the present invention.
Then, the compensation current command value (icomp**) obtained by
the additional compensator (60-2) is subtracted by the subtractor
(67) from the output of the original compensator (60-1). The output
of the subtractor (67) is supplied as a compensated value of the
second current command value (iT*) to the adder (53).
With such a configuration adopted, according to this embodiment,
the compensation is made based on not only the output current value
(|Iin|) of the converter circuit (11) but also the DC link voltage
(vdc) as well. Such additional compensation based on the DC link
voltage (vdc) may reduce the disturbance to be caused between the
supply voltage (Vin) and the DC link voltage (vdc), and may bring
the output current value (|Iin|) of the converter circuit (11) even
closer to the current command (|Iin*|).
Specifically, according to this embodiment, if the voltage of the
DC section (12) (i.e., the voltage at the input terminal of the
inverter circuit (13)) is greater than the command value (vdc*) of
the DC link voltage (vdc), the second current command value (iT*)
is compensated for such that the output power of the inverter
circuit (13) is further increased. On the other hand, if the DC
link voltage (vdc) is less than the command value (vdc*), the
second current command value (iT*) is compensated for such that the
output power of the inverter circuit (13) is further decreased.
As can be seen from the foregoing description, according to this
embodiment, the compensated value is obtained based on the stored
deviations (i.e., values correlated to a disturbance), and
therefore, the compensation may be done speedily.
<<Sixth Embodiment of This Invention>>
A sixth embodiment of the present invention to be described below
is a method of updating the deviation storage (62) differently from
any of the embodiments described above. FIG. 14 is a flowchart
showing how to update the deviation storage (62) according to the
sixth embodiment of the present invention. This embodiment provides
the flow shown in FIG. 14 by changing the compensator (60) of the
first embodiment. Note that the series of processing steps shown in
FIG. 14 are carried out after the current command (|Iin*|) and the
output current value (|Iin|) have been obtained within the carrier
period (Tc), and are performed repeatedly every carrier period
(Tc).
First of all, in the compensator (60), the first index generator
(63) generates an index (idx) indicating the storage location of
the deviation of this time in the deviation storage (62) (in Step
S11). The first index generator (63) calculates this index (idx)
based on the phase angle (.theta.in1). In this example,
idx=.theta.in1/(.pi./K) is satisfied, and the phase angle
(.theta.in1) is cleared every .pi.(i.e., every power supply half
period). Thus, the index (idx) generated by the first index
generator (63) increments one by one, and changes cyclically within
the range of 0 to K-1, as the phase angle (.theta.in1) increases
monotonically.
Next, the compensator (60) makes the subtractor (61) calculate the
deviation of the output current value (|Iin|) from the current
command (|Iin*|) (in Step S12).
Subsequently, the compensator (60) stores the deviation of this
time (i.e., the deviation obtained in Step S12) in any of the areas
of the deviation storage (62) associated with the index (idx) (in
Step S13). Note that when the deviation is stored, the moving
average between the deviation of this time and a past value stored
in the deviation storage (62) may be calculated and the result may
be stored instead of the deviation of this time.
The series of these three processing steps S11, S12, and S13 will
be performed repeatedly every carrier period (Tc) until the
deviation storage (62) obtains a predetermined number of (i.e., K
in this example) values to be stored. That is to say, according to
this embodiment, values correlated to a disturbance (i.e., the
current command (|Iin*|) and the output current value (|Iin|) in
this example) are sampled over multiple periods of the voltage
(Vin) of the AC power supply (30). In this manner, the deviation
storage (62) is allowed to obtain the predetermined number (i.e., K
in this example) of values to be stored.
As can be seen from the foregoing description, according to this
embodiment, values correlated to the disturbance are also stored in
the deviation storage (62) and the compensation current command
value (icomp*) to compensate for the second current command value
(iT*) may be generated based on those correlated values. Thus,
according to this embodiment, the distortion of the output current
of the converter circuit (11) (i.e., the distortion of an input
current to the inverter circuit (13)) caused by a disturbance with
a repetitive waveform such as LC resonance may also be reduced
easily and speedily. That is to say, the deviation of a current
from a command value thereof may also be reduced according to this
embodiment.
Particularly if the disturbance has a short variation period (i.e.,
too short to represent the variation in disturbance accurately by
making sampling every carrier period (Tc)), then it is recommended
that the deviation obtaining method of this sixth embodiment (see
FIG. 14) in which no interpolation is made intentionally with one
storage period (Tm) set to be shorter than one disturbance
variation period be adopted. In that case, not every data stored in
the deviation storage (62) is updated in a power supply half
period, but the data stored in the deviation storage (62) is
updated through sampling over multiple power supply half periods.
Thus, if the disturbance occurs repeatedly synchronously with a
power supply half period, the values correlated to the disturbance
may be stored accurately under the configuration of this sixth
embodiment.
<<Other Embodiments>>
Note that the control system of a power conversion device generally
includes a velocity control system. In that case, the magnitude of
compensation to be made by the compensator (60) may be set to be
zero when the power conversion device starts running.
Also, if it is known in advance that a significant variation in
load (e.g., when torque control needs to be performed synchronously
with either acceleration or deceleration of the motor (20) or the
rotational period of the motor (20)) should occur asynchronously
with a power supply period, the magnitude of compensation to be
made by the compensator (60) may be set to be zero.
Also, when the deviation of an output current value (|Iin|) from a
current command (|Iin*|) is calculated, the output current values
(|Iin|) over multiple power supply half periods may be averaged on
an index (idx) basis, and the deviation of the average value from
the current command (|Iin*|) may be obtained. The output current
values (|Iin|) may be averaged if the moving average of the output
current values (|Iin|) is obtained on an index (idx) basis, for
example. Note that if interpolation is made for the deviation
storage (62) as in the variation of the first embodiment,
non-averaged data is suitably used as data for interpolation.
In addition, the compensation based on the capacitor energy (Ce)
(see the second embodiment) does not always have to be carried out
in combination with the compensation based on the output current
value (|Iin|) (see the first and second embodiments). In other
words, in the second embodiment, the compensation based on the
output current value (|Iin|) may be omitted.
Furthermore, the power conversion device (10) does not have to
include the converter circuit (11) and the inverter circuit (13).
Optionally, the power conversion device (10) may also be
implemented as a so-called "matrix converter" configured to convert
an alternating current directly into an alternating current having
a predetermined frequency and a predetermined voltage.
Furthermore, the values correlated to the disturbance are not
limited to the exemplary ones adopted in the embodiments and their
variations described above. Alternatively, the correlated value may
also be a deviation of a current to a power converter (such as the
inverter circuit (13) or a matrix converter) from the command value
of the current to the power converter. Still alternatively, the
correlated value does not have to be a deviation but may also be a
current to a power converter (such as the inverter circuit (13) or
a matrix converter), the output current value (|Iin|) of the
converter circuit (11), the voltage (vdc) of the capacitor (12a),
or the energy of the capacitor (12a), for example.
Furthermore, the controller (50) may compensate for the q-axis
current command value (iq*) instead of the second current command
value (iT*).
INDUSTRIAL APPLICABILITY
The present invention is useful as a power conversion device.
DESCRIPTION OF REFERENCE CHARACTERS
10 Power Conversion Device
12a Capacitor
13 Inverter Circuit (Power Converter)
30 AC Power Supply
50 Controller (Power Conversion Controller)
60 Compensator (Power Conversion Controller)
62 Deviation Storage (Storage)
* * * * *